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  • 1. Ahmed, Aseel Bala
    et al.
    Jibril, B.
    Danwittayakul, S.
    Dutta, Joydeep
    Sultan Qaboos Univ, Water Res Ctr, Chair Nanotechnol, Muscat, Oman.
    Microwave-enhanced degradation of phenol over Ni-loaded ZnO nanorods catalyst2014In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 156-157, p. 456-465Article in journal (Refereed)
    Abstract [en]

    Nickel was loaded onto hydrothermally-grown ZnO nanorods on cordierite substrates and tested as catalysts in microwave-enhanced degradation of phenol from its aqueous solution (100 ppm) at 70 degrees C. Effects of metal loadings (1, 10 and 20 mM impregnation solutions) on the degradation of phenol in aqueous solution was investigated. The catalyst performances were monitored based on phenol degradation, product distributions and carbon dioxide (CO2) evolutions. Based on the type of the catalysts, two different mechanistic pathways for the decomposition were observed-through catechol and/or hydroquinone as intermediates. It was found that the 10mM nickel loaded sample catalyzed the degradation through one pathway with hydroquinone as the benzenediol intermediate formed, while the 20 mM nickel impregnated sample catalyzed the reaction through two pathways, producing catechol as well as hydroquinone by products. These differences in reaction pathways were attributed to the variation in the composition of the nickel compounds and surface structures between the two catalysts. Furthermore, the effect of hydrogen peroxide (H2O2) as an oxidant was explored. It was found that although addition of H2O2 led to an increase in the degree of phenol degradation, it also led to enhanced catalyst leaching. There was also an increase in CO2 evolution due to the addition of H2O2. It was observed that 20 mM nickel-loaded sample without the addition of H2O2 exhibited optimum performance in terms of phenol degradation and CO2 evolution with no drawback of catalyst leaching. Catalytic microwave enhanced degradation is an effective means for the removal of dissolved organic compounds from wastewater.

  • 2. Bergman, Susanna L.
    et al.
    Granestrand, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Tang, Yu
    Paris, Rodrigo Suarez
    Nilsson, Marita
    Tao, Franklin Feng
    Tang, Chunhua
    Pennycook, Stephen J.
    Pettersson, Lars J.
    Bernasek, Steven L.
    In-situ characterization by Near-Ambient Pressure XPS of the catalytically active phase of Pt/Al2O3 during NO and CO oxidation2018In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 220, p. 506-511Article in journal (Refereed)
    Abstract [en]

    This study concerns near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) studies of a Pt/A1203 diesel oxidation catalyst used in exhaust aftertreatment. We apply the technique to an industrial-grade porous catalyst, thus bridging both the pressure and materials gap, and probe the shift in binding energy of Pt 4d under different atmospheres. We observe that oxidizing atmospheres induce a shift in binding energy, corresponding to changes in Pt oxidation state, especially pronounced under an atmosphere of NO and O-2. Such changes in Pt oxidation state have previously been linked to dynamic changes in NO oxidation activity.

  • 3.
    Birgersson, Henrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Klingstedt, F
    Yu Murzin, D
    Stefanov, P
    Naydenov, A
    An investigation of a new regeneration method of commercial aged three-way catalysts2006In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 65, p. 93-100Article in journal (Refereed)
    Abstract [en]

    The ability to modify aged three-way catalysts (TWC) by regaining part of the fresh catalyst surface structure has been verified by both bulk and surface-sensitive characterisation techniques. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM/EDX) techniques were applied to fully evaluate the efficiency of a regeneration procedure of commercial three-way catalysts targeting the washcoat surface. The regeneration comprised combined thermal and liquid chlorine treatments. Structural changes of the washcoat were further investigated with nitrogen adsorption-desorption (BET) and Laser Ablation methods. The investigation showed that the regeneration treatments resulted in an enrichment of the washcoat surface with palladium, thereby increasing the number of catalytically active surface sites. Furthermore, the observed removal of phosphorous and sulphur contaminants resulted in an increase of the relative amount of small pores between 1 and 10 nm and washcoat surface area. An increased catalytic activity regarding CO, NOx, and HC emissions was observed after regeneration. providing proof of the proposed concept.

  • 4.
    Birgersson, Henrik
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Eriksson, L
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Järås, Sven
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Thermal gas treatment to regenerate spent automotive three-way exhaust gas catalysts (TWC)2004In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 54, p. 193-200Article in journal (Refereed)
    Abstract [en]

    The effect of regeneration on the metal dispersion and catalyst activity of commercial automotive three-way catalysts (TWC) in oxygen, hydrogen and oxy-chlorine at elevated temperatures has been investigated. In addition, characterisation of the catalysts has been performed using XRD, TEM, TPR, CO chemisorption and BET surface area measurements. Activity tests on monolith fragments were conducted in a micro-reactor supplied with real exhaust gases. An increase in activity was observed with oxygen treatment on catalysts showing heavy sintering as well as a high noble metal loading. Hydrogen proved to be an ineffective treatment procedure, whereas the addition of chlorine to the oxygen stream resulted in an activity increase even on catalysts less sintered and with lower noble metal contents. A comparison of the XRD and BET profiles showed no or small changes in the washcoat structure compared to fresh catalysts after successful regeneration. The TEM, TPR and CO chemisorption measurements suggest a decrease in the size of the largest noble metal agglomerates on the catalyst surface, as well as some Pd and RhO restructuring. The oxy-chlorine regeneration procedure is shown to be the most efficient, both regarding the catalyst activity and the metal dispersion. An increase in the amount of noble metal particles with a size of 20-70 nm, coupled with a decrease in size of larger clusters up to 100 nm in size, was observed for this treatment.

  • 5. Christou, Stavroula Y.
    et al.
    Birgersson, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Efstathiou, Angelos M.
    Reactivation of severely aged commercial three-way catalysts by washing with weak EDTA and oxalic acid solutions2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 71, no 3-4, p. 185-198Article in journal (Refereed)
    Abstract [en]

    Ethylene diamine tetraacetic acid (EDTA) which is a well-known reagent for its metal extraction efficiency was studied for the first time towards the improvement of the catalytic activity and oxygen storage and release properties (OSC) of severely aged commercial three-way catalysts (TWC) on a laboratory scale. Optimization of the experimental parameters of EDTA-washing procedure of TWC was carried out by varying the washing time, volumetric flow rate, and temperature of EDTA solution. The EDTA-washing procedure of TWC was compared with that of oxalic acid-washing regarding their efficiency in removing P, Pb, S, Ca, Zn, Fe, Cu, Cr, Ni, and Mn, all known TWC contaminants that many of them cause severe deterioration of TWC's activity and oxygen storage and release properties. EDTA appears to be significantly efficient in removing Pb, Zn, Ca, Mn, Fe, Cu and Ni metal contaminants and sulfur but not of phosphorus (P). Phosphorus-containing species were found to be efficiently removed from the aged TWCs after oxalic acid washing. All regeneration procedures applied led to a significant partial recovery of catalytic activity of TWC (CO, CxHy and NOx conversions) under real exhaust gas conditions (dynamometer tests) due to the removal of large amounts of contaminants accumulated on the aged TWC. The washing procedures using oxalic acid alone or in combination with EDTA led to more significant improvements of both catalytic and OSC performance compared with those of EDTA washing alone. This was due to the ability of oxalic acid to remove P-containing compounds which appear to be one of the main causes of commercial three-way catalyst deactivation. (C) 2006 Elsevier B.V. All rights reserved.

  • 6.
    Dahlin, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Nilsson, Marita
    Backstrom, Daniel
    Bergman, Susanna Liljegren
    Bengtsson, Emelie
    Bernasek, Steven L.
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Research Centre at Stellenbosch University, Stellenbosch, South Africa.
    Multivariate analysis of the effect of biodiesel-derived contaminants on V2O5-WO3/TiO2 SCR catalysts2016In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 183, p. 377-385Article in journal (Refereed)
    Abstract [en]

    This study investigates the effect of biodiesel-derived contaminants on vanadia-based NH3-SCR catalysts in heavy-duty exhaust aftertreatment. The aim was to study, not only the effect of single contaminants on the catalyst performance, but also of possible interaction effects between poisons. The effect of six potential catalyst poisons (Na, K, Mg, P, S and Zn) was evaluated using an experimental design and multivariate data analysis. Monolithic V2O5-WO3/TiO2 catalysts were subjected to accelerated laboratory-scale aging, where the six contaminants were fed simultaneously using a wet impregnation method. In addition to NO conversion tests, the catalysts were characterized by means of ICP-OES, SEM-EDX, XPS, N-2 physisorption and NH3-TPD. The lab-aged samples were compared to fresh and vehicle-aged catalysts. The accelerated aging method showed good reproducibility and gave rise to surface compounds similar to those found in vehicle-aged catalysts. Despite plausible differences regarding penetration depth of the contaminants into the walls of the catalyst, the aging method appears to be an efficient way to point out significant chemical poisons. The model obtained from the experimental design was found to correlate well with the experimental data and can therefore be used to predict effects of the various poisons and poison interactions. Significant effects on the NOx conversion were found for P, S, Na, Mg and K as well as for the interactions P x Na, P x K and S x Na. A poisoning effect was found for Mg, Na, K, P x K, and P x Na, where Na and K exhibited the strongest poisoning effect. The deactivating effect of alkali was lowered in the presence of phosphorus and sulfur, which is explained by the formation of phosphates and sulfates, preventing the interaction of the alkali metals with the vanadia active sites.

  • 7.
    Diesen, Veronica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Comment on the use of phenols as probes for the kinetics of heterogeneous photocatalysis2014In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 158, p. 429-431Article in journal (Refereed)
  • 8.
    Elm Svensson, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Stability of hexaaluminate-based catalysts for high-temperature catalytic combustion of methane2008In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 84, no 1-2, p. 241-250Article in journal (Refereed)
    Abstract [en]

    Lanthanum hexaaluminate with a nominal composition of LaAl11O18 Was used to support 20 wt.% of LaMnO3 and CeO2. LaAl11O18 was prepared through co-precipitation of metal nitrates within the water phase of an isooctane/CFAB/1-butanol microemulsion. The stabilities of the prepared catalysts were assessed by measuring the activities for combustion of methane before and after aging at 1000 degrees C for 100h in air with 10 vol.% H2O. The activities were compared with LaMnAl11O19, due to its well-documented stability. It was shown that by using hydrothermal treatment of the microemulsion, a significantly higher surface area was obtained for the LaAl11O18. For LaMnO3, the reference support (Al2O3) was shown to be superior to LaAl11O18 as support, both in terms of activity and stability. Reactions between LaMnO3 and support were observed for all supports included in the study. For CeO2, LaAl11O18 was superior to Al2O3 as support. Deactivations of the CeO2 catalysts were linked to crystal growth of CeO2. LMHA deactivated strongly during aging; LaMnO3 on Al2O3 and several of the catalysts with CeO2 supported on LaAl11O18 showed a much more stable behavior.

  • 9.
    Granlund, Moa Z.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Jansson, Kjell
    Stockholm University, Arrhenius Laboratory, Department of Materials and Environmental Chemistry.
    Nilsson, Marita
    Scania CV AB, Materials Technology, Engine Performance and Emissions.
    Dawody, Jazaer
    Volvo Group Trucks Technology, Advanced Technology & Research, Energy Efficiency & Environmen.
    Pettersson, Lars. J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Evaluation of Co, La, and Mn promoted Rh catalysts for autothermal reforming of commercial diesel2014In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 154, p. 386-394Article in journal (Refereed)
    Abstract [en]

    The objective of this paper was to study the influence three promoters (Co, La, Mn) had on the catalytic activity of Rh-based catalysts for autothermal reforming of diesel. The catalysts were supported on CeO2ZrO2 and the loading was 1 wt.% Rh and 6 wt.% promoter. The catalytic activity was evaluated in a monolith bench scale reactor with Swedish Environmental diesel, MK1. The process parameters employed at the ATR experiments were; O-2/C similar to 0.45, H2O/C similar to 2.5 and GHSV similar to 50,000h(-1), meanwhile the reactor temperature was ramped from 700 degrees C to 950 degrees C. The catalysts were compared based on their fuel conversion, H-2 yield and the selectivity of different short-chain hydrocarbons. The results showed that all three catalysts had both high fuel conversion and H-2 yield in the optimal ATR operation temperatures. The H-2 yield and fuel conversion were increasing in the order Rh/Mn, Rh/La, Rh/Co. To get further insight in the difference between the materials the fresh and aged catalytic materials were characterized. The characterization methods used were H-2-temperature programmed reduction (H-2-TPR), powder X-ray diffraction (XRD), and BET surface measurements. The BET surface measurements showed that promotion with La gave improved thermal stability of the material. The XRD showed a high dispersion of all metals except Co, which was present as crystals in the size range of the particles of the support.

  • 10.
    Granlund, Moa Z.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Jansson, Kjell
    Stockholm University.
    Nilsson, Marita
    Dawody, Jazaer
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Evaluation of Co, La, and Mn promoted Rh catalysts for autothermal reforming of commercial diesel: Aging and characterization2015In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 172, p. 145-153Article in journal (Refereed)
    Abstract [en]

    In this study three bimetallic catalysts are evaluated for autothermal reforming (ATR) of fuels (1 wt.% Rh and 6 wt.% X (X = Co, La or Mn) supported on high-surface area CeO2-ZrO2). The catalysts are aged for approximately 35 h and carefully characterized both as fresh and aged materials. The objective is to illuminate the changes in material properties after time on stream as well as the differences among the materials. The changes in material properties are evaluated by H2-TPR, BET surface area analysis, TEM, SEM and STEM. The material’s tendency to coke is investigated by TPO analysis.

    The three materials exhibit promising initial activity. However, the Co-promoted sample decreases sharply in activity after 25 h of operation. Meanwhile, the other two materials display a more stable activity throughout the evaluated time. The deactivation of the Co-promoted material could be linked to the high amount of coke deposited during operation. Based on the results from the activity evaluation and characterization, the material promoted with lanthanum displays the most promising results. The addition of lanthanum resulted in a catalyst that was both stable and had high activity, even though a low rhodium loading is used. The material also shows superior thermal resistance compared to the other two materials. In addition, the tendency to coke is significantly lower compered to the other materials, which is especially beneficial when dealing with ATR of complex fuels. 

  • 11.
    Gunnarsson, Fredrik
    et al.
    Chalmers Tekniska Högskola.
    Granlund, Moa. Z.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Englund, Mattias
    Chalmers Tekniska Högskola.
    Dawody, Jazaer
    Pettersson, Lars. J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Härelind, Hanna
    Chalmers Tekniska Högskola.
    Combining HC-SCR over Ag/Al2O3 and hydrogen generation over Rh/CeO2-ZrO2 using biofuels: An integrated system approach for real applications2015In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 162, p. 583-592Article in journal (Refereed)
    Abstract [en]

    Abstract We report on a high NOx reduction activity over Ag/Al2O3 catalysts, using hydrogen produced in a fuel reformer. The focus of the study is to evaluate the performance of a hydrocarbon selective catalytic reduction (HC-SCR) catalyst in real conditions. Initially, the catalytic materials for the fuel reformer (Rh/CeO2-ZrO2) and the HC-SCR (Ag/Al2O3) were evaluated in separate bench-scale reactor setups. These two setups were subsequently joined into an integrated bench-scale reactor setup with the aim to evaluate the influence of the reformate on the HC-SCR activity in a controlled environment. In the final phase of the study a 4 wt.% Ag/Al2O3 catalyst doped with 100 ppm(w) Pt was scaled up and tested in a pilot-scale reactor setup. The pilot-scale reactor setup enabled evaluation of the HC-SCR activity in real exhaust gases generated by a single cylinder engine (genset) together with a hydrogen-rich gas supplied from a fuel reformer. Commercial biodiesel (NExBTL) was used as reducing agent for the HC-SCR as well as fuel in the fuel reformer for both the bench-scale and pilot-scale experiments. This study gives an excellent link between evaluations of the catalytic materials, controlled bench-scale experiments and applied engine experiments, proving a viable concept for lean NOx reduction together with onboard hydrogen production. A NOx conversion of above 70% was reached at temperatures below 250 °C, in bench-scale experiments when hydrogen produced in the fuel reformer is added.

  • 12.
    Haghighi Moud, Pouya
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Andersson, Klas J.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Equilibrium potassium coverage and its effect on a Ni tar reforming catalyst in alkali- and sulfur-laden biomass gasification gases2016In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 190, p. 137-146Article in journal (Refereed)
    Abstract [en]

    Biomass conversion to syngas via gasification produces certain levels of gaseous by-products, such as tar and inorganic impurities (sulfur, potassium, phosphorus etc.). Nickel, a commonly used catalyst for hydrocarbqn steam reforming, suffers reduced reforming activity by small amounts of sulfur (S) or potassium (K), while resistance against deleterious carbon whisker formation increases. Nevertheless, the combined effect of biomass derived gas phase alkali at varying concentrations together with sulfur on tar reforming catalyst performance under realistic steady-state conditions is largely unknown. Prior to this study, a methodology to monitor these effects by precise K dosing as well as K co-dosing with S was successfully developed. A setup consisting of a 5 kW biomass fed atmospheric bubbling fluidized bed gasifier, a high temperature hot gas ceramic filter, and a catalytic reactor operating at 800 degrees C were used in the experiments. Within the current study, two test periods were conducted, including 30 h with 1 ppmv potassium chloride (KCl) dosing followed by 6 h without KCl dosing. Besides an essentially carbon-free operation, it can be concluded that although K, above a certain threshold surface concentration, is known to block active Ni sites and decrease activity in traditional steam reforming, it appears to lower the surface S coverage (theta(s)) at active Ni sites. This reduction in theta(s) increases the conversion of methane and aromatics in tar reforming application, which is most likely related to K-induced softening of the S-Ni bond. The K-modified support surface may also contribute to the significant increase in reactivity towards tar molecules. In addition, previously unknown relevant concentrations of K during realistic operating conditions on typical Ni-based reforming catalysts are extrapolated to lie below 100 mu K/m(2), a conclusion based on the 10-40 mu K/m(2) equilibrium coverages observed for the Ni/MgAl2O4 catalyst in the present study.

  • 13. Kannisto, H.
    et al.
    Karatzas, Xanthias
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Edvardsson, J.
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Ingelsten, H. H.
    Efficient low temperature lean NOx reduction over Ag/Al2O3-A system approach2011In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 104, no 1-2, p. 74-83Article in journal (Refereed)
    Abstract [en]

    This study focuses on lean NOx reduction (LNR) by n-octane using silver-alumina based catalysts, with the addition of hydrogen. The work takes a system approach, where parameters such as temperature, reformate gas composition, fuel penalty and realistic monolith samples are considered. The LNR catalyst samples were prepared by impregnation and sol-gel methods and the NOx reduction performance was characterized by flow-reactor experiments, where realistic engine-out gas compositions were used. The hydrogen feed over the LNR catalyst samples was determined via data achieved by autothermal reforming experiments over a rhodium based catalyst, using real diesel as feedstock. The LNR catalyst samples generally show an enhanced NOx reduction when hydrogen is added to the gas feed. In particular, a 2 wt% silver-alumina sample with the addition of minute amounts of platinum, shows a high increase in NOx reduction when hydrogen is added to the feed. The addition of CO, a potential poison in the reaction and a by-product from the reforming, did not show any significant effect on the LNR catalyst performance at the conditions used. This is beneficial, since it renders a CO clean-up step in the reformer system unneeded. Ammonia formation is discussed in terms of a possible dual-SCR system. Finally, the fuel penalty for hydrogen production and hydrocarbon addition is taken into consideration. It is found that an addition of 1000 ppm H-2 leads to unacceptable fuel penalties.

  • 14.
    Karatzas, Xanthias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Dawody, Jazaer
    Grant, Ann
    Svensson, Erik Elm
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Zone-coated Rh-based monolithic catalyst for autothermal reforming of diesel2011In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 101, no 3-4, p. 226-238Article in journal (Refereed)
    Abstract [en]

    In this work we present results of hydrogen generation from diesel via autothermal reforming (AIR) obtained with monolithic catalysts consisting of either one or two layers of monometallic Rh and bimetallic RhPt washcoats. The Rh metal loading of the monometallic washcoats was varied between 0.5, 1.0 and 3.0 wt%, while the weight ratio of Rh:Pt in the bimetallic washcoats was kept constant at 1:1. Furthermore, non-doped and CeLa-doped catalysts were also tested to detect differences in catalyst activity. The catalysts consisting of two layers of washcoats were termed zoned catalysts and each layer was applied to some given length in the axial direction of the monolith. All catalysts were prepared by impregnation using the incipient wetness technique with delta-Al2O3 B as support and deposited onto 400 cpsi cordierite monoliths. A total of eight catalysts, including both single layered and zone-coated, were tested in a bench-scale reactor using low-sulfur diesel as fuel at operating conditions H2O/C=2.5, O-2/C=0.49 (lambda = 0.33), GHSV 17,000 h(-1) and P = 1 atm. The results showed that the zoned catalyst, covered with the two washcoats Rh1.0Pt1.0-Ce10La5.0/delta-Al2O3 and Rh-3.0-Ce10La10/delta-Al2O3, respectively, was most active in terms of fuel conversion and hydrogen production. The zoned catalyst's long-term performance and stability was also evaluated in a full-scale reactor using low-sulfur and Fischer-Tropsch diesels at operating conditions H2O/C = 2.5, O-2/C = 0.49 (lambda =0.33), GHSV= 10,800 h(-1), P = 1 atm, and at H2O/C = 2.4, 02/C = 0.39 (lambda=0.26), GHSV- 10,200 h(-1), P = 1 atm. respectively. The results showed that high fuel conversion and hydrogen production were obtained from both fuels. In addition, partial oxidation and steam reforming reactions were identified by closely studying the distribution of the analyzed product gas composition and the temperature measurements. Fresh and aged samples of the catalysts were characterized by N-2-BET, H-2 chemisorption, XRD, H-2-TPR, O-2-TPO and XPS analyses.

  • 15.
    Karatzas, Xanthias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Jansson, Kjell
    Stockholm University.
    González, Angélica
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Dawody, Jazaer
    Volvo Technology.
    Pettersson, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Autothermal reforming of low-sulfur diesel over bimetallic RhPt supported on Al2O3, CeO2-ZrO2, SiO2 and TiO22011In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 106, no 3-4, p. 476-487Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to study and clarify the role of selected supports (both reducible and non-reducible) on the activity, selectivity and stability of RhPt-based catalyst for diesel reforming. Autothermal reforming (AIR) of low-sulfur diesel (S similar to 6 ppm, C/H similar to 6.43 (w/w)), H(2)O/C similar to 2.5, O(2)/C similar to 0.49, was tested at bench scale to detect differences in activity for catalysts consisting of 1 wt% Rh and 1 wt% Pt supported on alumina, ceria-zirconia (17.5 wt% ceria), silica and titania. Promoters in the form of MgO. Y(2)O(3), La(2)O(3), CeO(2) and ZrO(2), ranging from 4 wt% to 10 wt%, were also added onto the supports to detect differences in catalyst activity in terms of diesel conversion, CO(2) selectivity, and hydrogen and ethylene production. All metals were added sequentially onto the support by the incipient wetness technique and washcoated on 400 cpsi cordierite monolithic carriers with dimensions d = 17.8 mm, l=30.5 mm.

    The product gas analysis, using FTIR and NDIR, showed that RhPt/CeO(2)-ZrO(2) was found to be most active for AIR of diesel since a fuel conversion close to 98% was obtained. Furthermore, the catalyst activity of the unpromoted samples, in terms of diesel conversion, increased in the following order: RhPt/SiO(2) < RhPt/TiO(2) < RhPt/Al(2)O(3) < RhPt/CeO(2)-ZrO(2). The addition of promoters was found to be insignificant as well as having a negative impact on the catalyst performance in most cases, except for the alumina-promoted sample. The addition of 10 wt% La(2)O(3) on RhPt/Al(2)O(3) was found to enhance diesel conversion, hydrogen productivity as well as lower the ethylene concentration from 3700 ppm to less than half that value. The latter observation was confirmed by O(2)-TPO analysis of aged powder samples where lower loads of coke were present than on the La-promoted sample.

    The morphology, surface and bulk properties of RhPt/CeO(2)-ZrO(2) were closely examined in order to provide a possible correlation between the activity and characterization results. N(2)-BET analysis showed that the surface area of RhPt/CeO(2)-ZrO(2) was 64 m(2)/g, while the silica samples exhibited the highest area, similar to 137-185 m(2)/g. Hence, the difference in the surface areas was not enough to explain the trends observed in the activity measurements. XRD analysis of RhPt/CeO(2)-ZrO(2) showed crystalline phases characteristic of zirconia, most likely tetragonal. Also, the diffractogram did not reveal any Rh or Pt peaks indicating that the noble metal particles are highly dispersed on the support. In contrast, peaks ascribed to metallic Pt (similar to 30-46 nm) were clearly visible on the XRD patterns taken from all the other supported samples. H(2)-TPR analysis of RhPt/CeO(2)-ZrO(2) showed reduction peaks ascribed to Rh(i)O(x) species as well as a minor hydrogen spillover effect on the support to be present at T=120 degrees C and 450 degrees C, respectively. Also, the hydrogen consumption of the Rh(i)O(x) species was the highest compared to the other supported RhPt samples. TEM analysis performed on fresh RhPt/CeO(2)-ZrO(2) showed that the Rh(i)O(x) and Pt particles were highly dispersed on the support, both with particle sizes in the vicinity of similar to 5-15 nm. Rh species was found on ceria and zirconia, while Pt was present mainly on the ceria layer possibly in the form of Pt-O-Ce bonds. H(2)-chemisorption analysis measured at T similar to 40 degrees C shows similar Rh dispersion results.

    To summarize, the higher activity results of RhPt/CeO(2)-ZrO(2) for AIR of diesel, compared to other supported catalysts, may be ascribed to the higher reducibility of Rh(i)O(x) species as well as the superior Rh and Pt dispersion. Also, the support contribution, in particular ceria, is believed to promote water gas-shift activities as well as reduce coke deposits on the catalyst surface.

  • 16. Kling, Asa
    et al.
    Andersson, Christer
    Myringer, Ase
    Eskilsson, David
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Alkali deactivation of high-dust SCR catalysts used for NOx reduction exposed to flue gas from 100 MW-scale biofuel and peat fired boilers: Influence of flue gas composition2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 69, no 04-mar, p. 240-251Article in journal (Refereed)
    Abstract [en]

    Deactivation of vanadium-titanium deNO(x) SCR (selective catalytic reduction) catalysts in high-dust position have been investigated in three 100 MW-scale boilers during biofuel and peat combustion. The deactivation of the catalyst samples has been correlated to the corresponding flue gas composition in the boilers. Too investigate the effect on catalyst deactivation a sulphate-containing additive was sprayed into one of the furnaces. Increased alkali content on the SCR catalyst samples decreased the catalytic deNO(x), activity. The study has shown a linear correlation between exposure time in the boilers and alkali concentration (mainly potassium) on the samples. The results imply that mainly alkali in ultra fine particles (< 100 nm) in the flue gas increased the alkali accumulation on the catalyst samples. Low correlation was found between particles larger than 100 nm and the catalyst deactivation. It was not possible to decrease the deactivation of the catalyst samples by the sulphate-containing additive. Although the additive had an effect in sulphating potassium chloride to potassium sulphate, it did not decrease the amount of potassium in ultra fine particles or the deactivation of the catalyst samples.

  • 17. Kusar, H. M. J.
    et al.
    Ersson, A. G.
    Järås, Sven G.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Catalytic combustion of gasified refuse-derived fuel2003In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 45, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    The catalytic combustion of gasified refuse-derived fuel (RDF), i.e. a low heating-value (LHV) gas containing H-2, CO and CH4 as combustible components, has been studied and compared with the combustion of methane. Two metal oxide catalysts, i.e. a spinel and a hexaaluminate, and three noble metal catalysts were tested. The results show that the Pd-based catalysts were the most active both for the gasified waste, i.e. RDF and methane. Incorporating an active support such as LaMnAl11O19 enhances the catalytic activity for methane in gasified waste. Substituting Mn into the crystal lattice of the spinel also increased the catalytic activity for H-2 and CO, while the methane activity remained low. The formation of NOX from fuel-bound nitrogen was investigated by adding NH3 to the gas stream. The metal oxide catalysts showed a higher selectivity for oxidising NH3 into N-2 than the catalysts containing precious metals. The spinel materials have high thermal stability and are comparable to the hexaaluminates confirming that they could be promising as washcoat materials to avoiding sintering at high temperatures.

  • 18. Kusar, H. M. J.
    et al.
    Ersson, A. G.
    Vosecky, M.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Selective catalytic oxidation of NH3 to N-2 for catalytic combustion of low heating value gas under lean/rich conditions2005In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 58, no 02-jan, p. 25-32Article in journal (Refereed)
    Abstract [en]

    The selective catalytic oxidation (SCO) of ammonia to nitrogen has been examined over 5% Fe/Al2O3, 5% Mn/Al2O3, 20% Cuo/Al2O3, 1% Pt/20% CuO/Al2O3, 2% Rh/Al2O3 and a Fe zeolite (Fe-SH-27) under fuel-lean and fuel-rich conditions in a monolith lab-scale reactor. For simulating fuel-bound nitrogen in a low heating value (LHV) gas 400 ppm NH3 was added to the test gas. The SCO performance of the catalysts was tested both with and without water added to the gas stream. For SCO under fuel-lean conditions the Fe-zeolite catalyst exhibited the lowest NO, yield. For SCO under fuel-rich conditions the 20% CuO/Al2O3 was superior with close to zero NO, formation.

  • 19.
    Kusar, Henrik
    et al.
    Laboratory of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Ljubljana, Slovenia.
    Hocevar, S.
    Laboratory of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Ljubljana, Slovenia.
    Levec, J.
    Laboratory of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Ljubljana, Slovenia.
    Kinetics of the water-gas shift reaction over nanostructured copper-ceria catalysts2006In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 63, no 3-4, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Water–gas shift reaction was studied over two nanostructured CuxCe1−xO2−y catalysts: a Cu0.1Ce0.9O2−ycatalyst prepared by a sol–gel method and a Cu0.2Ce0.8O2−y catalyst prepared by co-precipitation method. A commercial low temperature water–gas shift CuO–ZnO–Al2O3 catalyst was used as reference. The kinetics was studied in a plug flow micro reactor at an atmospheric pressure in the temperature interval between 298 and 673 K at two different space velocities: 5.000 and 30.000 h−1, respectively. Experimentally estimated activation energy, Eaf, of the forward water–gas shift reaction at CO/H2O = 1/3 was 51 kJ/mol over the Cu0.1Ce0.9O2−y, 34 kJ/mol over the Cu0.2Ce0.8O2−y and 47 kJ/mol over the CuO–ZnO–Al2O3 catalyst. A simple rate expression approximating the water–gas shift process as a single reversible surface reaction was used to fit the experimental data in order to evaluate the rate constants of the forward and backward reactions and of the activation energy for the backward reaction.

  • 20. Laguna, O. H.
    et al.
    Centeno, M. A.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Odriozola, J. A.
    Fe-doped ceria solids synthesized by the microemulsion method for CO oxidation reactions2011In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 106, no 3-4, p. 621-629Article in journal (Refereed)
    Abstract [en]

    A series of Ce-Fe mixed oxides as well as the pure oxides were synthesized by the microemulsions method. The solid solution formation was established for all the Fe-doped systems and only a hardly noticeable segregation of alpha-Fe(2)O(3) was appreciated for the solid with the maximum iron content (50 at.% Fe). The oxygen exchange is improved for all the Fe-doped systems; however the 10 at.% Fe appears as the optimal iron content for achieving the maximum oxygen vacancies concentration and the higher reducibility efficiency. The CO oxidation (TOX. PROX) is especially achieved for the solids with the lower iron contents but with a superior oxygen vacancies proportion. These Ce-Fe systems prepared from microemulsions are very attractive to be considered as supports for depositing active phases capable of enhancing oxygen exchange ability of the whole system, allowing higher CO oxidation abilities.

  • 21. Li, F.
    et al.
    Wang, Y.
    Du, J.
    Zhu, Y.
    Xu, C.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology, Dalian, 116024, China.
    Simultaneous oxidation of alcohols and hydrogen evolution in a hybrid system under visible light irradiation2018In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 225, p. 258-263Article in journal (Refereed)
    Abstract [en]

    Water oxidation as a multi-electron transfer and endothermal reaction has been considered to be the bottleneck of solar-driven water splitting into oxygen and hydrogen. Herein, an alternative approach for solar energy conversion is developed by coupling H2 generation with the selective oxidation of alcohol. In a closed redox system containing molecular ruthenium catalyst (RuCat) and Pt modified g-C3N4 (Pt-g-C3N4) composite, hydrogen production is concomitant with the oxidation of benzyl alcohols to aldehydes with over 99% selectivity in the presence of visible light and pure water. By contrary, the system lacking molecular catalyst only exhibits low to moderate selectivities towards aldehydes. The remarkably improved selectivity is attributed to the formation of highly active Ru(IV) = O intermediate through efficient hole transfer from g-C3N4 to RuCat.

  • 22.
    Lögdberg, Sara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Tristantini, Dewi
    Chalmers Tekniska högskola.
    Borg, Öyvind
    Norwegian University of Science and Technology (NTNU).
    Ilver, Lars
    Chalmers Tekniska högskola.
    Gevert, Börje
    Chalmers Tekniska högskola.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Blekkan, E.A
    Norwegian University of Science and Technology (NTNU).
    Holmen, Anders
    Hydrocarbon production via Fischer-Tropsch synthesis from H-2-poor syngas over different Fe-Co/gamma-Al2O3 bimetallic catalysts2009In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 89, no 1-2, p. 167-182Article in journal (Refereed)
    Abstract [en]

    Fischer-Tropsch synthesis (FTS) at 20 bar. and 483 K, with H-2-poor syngas (H-2/CO ratio = 1.0) in order to simulate gasified biomass, was performed over Al2O3-supported catalysts with various ratios of Fe:Co (12 wt% bimetal) prepared by co-impregnation. Co was found to be incorporated into the Fe2O3 phase after calcination, at least for the iron-rich samples, while no evidence of Fe incorporated into Co3O4 was found. Upon reduction, most probably FeCo alloys were formed in the iron-rich bimetallic samples. The degree of reduction of the catalysts showed a non-linear behavior with respect to the Fe:Co ratio, but it is obvious that Co increases the reducibility of Fe. Alloying Co with small/moderate amounts of Fe improved the FT activity compared to the 100% Co catalyst at low conversion levels. Alloying Fe with small/moderate amounts of Co lowered the FT activity, but increased the relative water-gas-shift (WGS) activity compared to the 100% Fe catalyst. However, the overall WGS activity was very low for all catalysts, even with external water addition to the feed, resulting in low FT productivities (per gram catalyst) due to the low partial pressure of H-2. A higher Fe:Co ratio in the bimetallic catalyst generally resulted in higher relative WGS activity, but did not lower the H-2/CO usage ratio to the desired value of 1.0. For the Fe-containing catalysts, the space-time yield of hydrocarbons (HCs) decreased with increasing partial pressure of water or reduced space velocity, indicating an inhibition of water on the FT activity, most often resulting in low FT productivity under the conditions with highest relative WGS activity (usage ratios closest to the inlet H-2/CO ratio). Moreover, the co-impregnation technique resulted in a surface enrichment of Fe, at least for the Co-rich samples, covering the Co sites. For the bimetallic catalysts, both FT and WGS activities rapidly declined at high partial pressure of water due to deactivation by oxidation and sintering. However, the results indicate that WGS and FT proceeded over sites of different nature in the bimetallic catalysts.The bimetallic catalysts showed essentially no synergy effects with respect to HC selectivities and olefin/paraffin ratios, which partly can be explained by the use of a sub-stoichiometric H-2/CO ratio as feed. The higher the Fe content, the lower were the C5+ selectivity and C-3 olefin/paraffin ratio. Water addition increased the C5+ selectivity and C-3 Olefin/paraffin ratio and reduced the CH4 selectivity.

  • 23. Nassos, S.
    et al.
    Svensson, E. Elm
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    The influence of Ni load and support material on catalysts for the selective catalytic oxidation of ammonia in gasified biomass2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 74, no 1-2, p. 92-102Article in journal (Refereed)
    Abstract [en]

    The effect of nickel (Ni) load (0, 5 and 10 wt.%) and support material (Ce0.9La0.1O2, Ce0.9Zr0.1O2 and gamma-Al2O3), together the amount of oxygen (lambda = 0.25 and lambda = 0.5) and gas hourly space velocity (50 000, 100 000 and 150 000 h(-1)) were investigated for the selective catalytic oxidation of ammonia in gasified biomass. The mixed metal oxide support materials were prepared by microemulsion, whereas the alumina was a commercial product. Ni was added to the different supports by incipient wetness. All the obtained catalysts were characterised by BET and XRD analysis. Cordierite monoliths coated with 20 wt.% catalytic material were tested in a tubular quartz reactor. For simulating the gasified biomass fuel, 500 ppm of NH3 was added to the fuel. Water was also present during the activity tests, which were carried out between 500 and 750 degrees C. The results from the activity tests at lambda = 0.25 and gas hourly space velocity of 100 000 h(-1) indicated that the 10 wt.% Ni on Ce0.9La0.1O2 was the best catalyst obtaining 65 and 97% N-2 yield at 500 and 750 degrees C, respectively. By increasing lambda to 0.5 and decreasing the gas hourly space velocity, the N-2 yield improved considerably at low temperature level (500 degrees C). Moreover, NOx emissions maintained at low levels depending on the experimental conditions. Constant conversion and negligible carbon deposition were also two other important observations from the mixed metal oxide supported catalysts. On the contrary, all the alumina-based catalysts displayed the lowest performance.

  • 24.
    Nassos, Stylianos
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Svensson, Erik Elm
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nilsson, M.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Microemulsion-prepared Ni catalysts supported on cerium-lanthanum oxide for the selective catalytic oxidation of ammonia in gasified biomass2006In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 64, no 02-jan, p. 96-102Article in journal (Refereed)
    Abstract [en]

    Nickel (Ni) catalysts supported on cerium-lanthanum oxide were prepared by two different preparation techniques and have been tested in the temperature range of 500-750 degrees C for selective catalytic oxidation of ammonia to nitrogen in gasified biomass. The two different catalyst preparation methods used are the conventional and the microemulsion (water-in-oil). The effect on catalytic activity of different Ni loadings was also tested in combination with the preparation method. Catalyst characterisation was focused on BET and XRD analysis. Cordierite monoliths were used in a tubular quartz reactor for the purpose of the activity tests. For simulating the gasified biomass fuel, 400 ppm NH3 was added to the fuel. Water was also present during the activity tests, which were carried out at fuel rich conditions. Results showed that the microemulsion-prepared catalysts obtained higher performance than the conventional ones, with the best catalyst reaching 98% ammonia conversion and 99% nitrogen selectivity at 750 degrees C. The more the Ni supported on the catalyst, the higher the catalytic activity. Constant conversion and negligible carbon deposition were two other important characteristics for the microemulsion-prepared catalysts.

  • 25.
    Nilsson, Marita
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Jansson, Kjell
    Jozsa, Peter
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Catalytic properties of Pd supported on ZnO/ZnAl2O4/Al2O3 mixtures in dimethyl ether autothermal reforming2009In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 86, p. 18-26Article in journal (Refereed)
    Abstract [en]

    The catalytic properties of Pd supported on mixtures of zinc oxide, zinc aluminate, and alumina, prepared from gamma-alumina and zinc nitrate, were studied for autothermal reforming (ATR) of dimethyl ether (DME). The performance of the catalysts was tested in a small-scale reactor, using cordierite monoliths as substrate. The catalysts exhibited high activity and generated hydrogen-rich product gases with CO concentrations below 5 vol.% in the temperature range between 350 and 450 degrees C (at O-2:DME = 0.7, H2O:DME = 2.5, and GHSV = 15000 h(-1)). The highest DME conversion was obtained for a catalyst in which the support comprised mainly ZnAl2O4. Physical mixing of the catalysts with gamma-Al2O3 resulted in increased DME conversion but a lowering of the CO2 selectivity.The catalysts were characterized by CO chemisorption, liquid nitrogen adsorption, temperature-programmed desorption of ammonia, temperature-programmed reduction, transmission electron microscopy, and X-ray diffraction. It was found that decreasing surface area and decreasing number of acid sites, caused by thermal treatment during generation of the supports, did not affect the activity negatively. The high CO2 selectivity of the catalysts was correlated with PdZn alloy formation.

  • 26.
    Nilsson, Marita
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Jozsa, Peter
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Evaluation of Pd-based catalysts and the influence of operating conditions for autothermal reforming of dimethyl ether2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 76, p. 41-49Article in journal (Refereed)
    Abstract [en]

    A series of different Pd-based catalysts supported on ceramic monoliths were synthesized and tested in a screening study for autothermal reforming of dimethyl ether (DME). Alumina-supported Pd was shown to be very active for this reaction at temperatures between 350 and 400 degrees C. Adding Zn to Pd/gamma-Al2O3 decreased the activity of decomposition reactions leading to better reforming activity, and resulting in high selectivity to carbon dioxide. Pd-Zn/gamma-Al2O3 was further evaluated in a parameter study varying oxygen-to-DME ratio, steam-to-DME ratio and temperature. The effect on the reformer performance of changing the operating conditions is discussed. The Pd-Zn/gamma-Al2O3 catalyst generated carbon monoxide concentrations below 5%, and hydrogen concentrations close to 50%. The catalyst performance was significantly improved by preconditioning in hydrogen. Results from a first round of catalyst characterization studies suggest that Pd-Zn species are formed on the alumina support following reduction

  • 27.
    Persson, Katarina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Pfefferle, Lisa D.
    Schwartz, William
    Ersson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Stability of palladium-based catalysts during catalytic combustion of methane: The influence of water2007In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 74, no 3-4, p. 242-250Article in journal (Refereed)
    Abstract [en]

    The stability of methane conversion was studied over a Pd/Al2O3 catalyst and bimetallic Pd-Pt/Al2O3 catalysts. The activity of methane combustion over Pd/Al2O3 gradually decreased with time, whereas the methane conversion over bimetallic Pd-Pt catalysts was significantly more stable. The differences in combustion behavior were further investigated by activity tests where additional water vapor was periodically added to the feed stream. From these tests it was concluded that water speeds up the degradation process of the Pd/Al2O3 catalyst, whereas the catalyst containing Pt was not affected to the same extent. DRIFTS studies in a mixture of oxygen and methane revealed that both catalysts produce surface hydroxyls during combustion, although the steady state concentration on the pure Pd catalyst is higher for a fixed temperature and water partial pressure. The structure of the bimetallic catalyst grains with a PdO domain and a Pd-Pt alloy domain may be the reason for the higher stability, as the PdO domain appears to be more affected by the water generated in the combustion reaction than the alloy. Not all fuels that produce water during combustion will have stability issues. It appears that less strong binding in the fuel molecule will compensate for the degradation.

  • 28. Requies, J.
    et al.
    Alvarez-Galvan, M. C.
    Barrio, V. L.
    Arias, P. L.
    Cambra, J. F.
    Güemez, M. B.
    Manrique Carrera, Arturo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    de la Peña O'Shea, V. A.
    Fierro, J. L. G.
    Palladium-manganese catalysts supported on monolith systems for methane combustion2008In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 79, no 2, p. 122-131Article in journal (Refereed)
    Abstract [en]

    Alumina-supported bimetallic and monometallic Mn and Pd monolithic catalysts were prepared and tested in methane combustion. Two different reactor configurations were adopted for catalyst testing, i.e. a fixed-bed laboratory-scale reactor and a pilot-plant reactor which allowed work at different temperatures and pressures. The results of catalyst performance showed that all bimetallic catalysts are considerably more stable for methane combustion than the monometallic palladium catalyst. With the aim to explain the relationship between activity-stability and structure and surface properties, the catalysts were characterized by TPO, XRD, XPS and ICP-AES. The high stability displayed by the bimetallic systems is attributed to the influence of manganese in retarding the decomposition of PdO into metallic palladium. Thus, it appears that manganese oxides inhibit PdO decomposition, as a consequence of the increase in oxygen mobility in the manganese oxide spinel phase.

  • 29. Samu, G. F.
    et al.
    Veres, ?.
    Endrődi, Balázs
    University of Szeged, Hungary.
    Varga, E.
    Rajeshwar, K.
    Janáky, C.
    Bandgap-engineered quaternary MxBi2-xTi2O7 (M: Fe, Mn) semiconductor nanoparticles: Solution combustion synthesis, characterization, and photocatalysis2017In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 208, p. 148-160Article in journal (Refereed)
    Abstract [en]

    Ternary and quaternary metal oxides form a rapidly emerging class of new functional materials tackling the grand challenge of efficient solar energy harvesting. Currently the main interest is devoted to the characteristics of these materials and little consideration has been given to their preparation. Solution combustion synthesis (SCS) is considered a green and sustainable alternative to the widely employed energy-and/or time-consuming synthesis methods. In this study, SCS was employed to prepare Bi2Ti2O7 and to perform bandgap engineering through foreign ion (Fe, Mn) incorporation. The synthesized materials were characterized by powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray microanalysis, diffuse reflectance UV-vis and Raman spectroscopy, and surface area determination via N-2 adsorption. We found that nanocrystalline materials were formed during the SCS synthesis. Further, the phase composition of these materials and the amount of the foreign metal ions incorporated in the parent structure, could be effectively controlled. Consequently, the SCS technique provided a simple and reliable tool for bandgap engineering. The photocatalytic activity of the materials was tested through methyl orange degradation, and the intrinsic photocatalytic activity of the various samples were compared after deconvoluting the effect of their vastly different specific surface areas.

  • 30.
    Scarabello, Andrea
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Dalle Nogare, D.
    Canu, P.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Partial oxidation of methane on Rh/ZrO2 and Rh/Ce-ZrO2 on monoliths: Catalyst restructuring at reaction conditions2015In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 174-175, p. 308-322Article in journal (Refereed)
    Abstract [en]

    0.5% Rh catalysts on ZrO2 or CeO2-ZrO2, coated on monoliths were tested for partial oxidation of methane, (GHSV=100000h-1). We ran temperature cycles up to 850°C, varying the O2/CH4 ratio from 0.5 to 0.7. The catalysts were characterized by XRD, TPR/TPO, BET and chemisorption. ZrO2 required a long conditioning step, to reach stable performance, while the CeO2-ZrO2 catalyst quickly gained steady activity. The conditioning step is explained with a restructuring of the surface, with the metallic particles becoming smaller. Ceria lowers the ignition temperature by 60°C. At low temperature, ceria allows an increase in CH4 conversion and selectivity to syngas. At high temperature, the CeO2-ZrO2 catalyst significantly increases the CH4 conversion, compared to ZrO2, approaching 100%. However, the selectivity to syngas decreases below 80%. The syngas selectivity is higher at lower O2/CH4 ratio, at any temperature, but the absolute amount of syngas can be larger with more O2.

  • 31.
    Ye, Lu
    et al.
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Gao, Yan
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Cao, Shuyan
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Chen, Hu
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Yao, Yanan
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Hou, Jungang
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Assembly of highly efficient photocatalytic CO2 conversion systems with ultrathin two-dimensional metal-organic framework nanosheets2018In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 227, p. 54-60Article in journal (Refereed)
    Abstract [en]

    An ultrathin two-dimensional Zn porphyrin-based metal-organic framework (Zn-MOF nanosheets) is developed and used for the first time in photoreduction of CO2 to CO. Consequently, two novelty noble-metal-free hybrid photocatalytic systems are established and displayed outstanding photocatalytic activity and selectivity for CO evolution under mild photocatalytic reaction conditions. The insight revealed Zn-MOF nanosheets as photo sensitizer displays a better charge transport ability and longer lifetime of the photogenerated electron-hole pairs than the Zn-MOF bulk, which are confirmed by photoelectrochemical impedance and photoluminescence (PL) measurements. These studies show that the development of noble-metal-free photocatalytic systems and various MOF-based materials for photocatalytic applications are promising.

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